tools/cgroup/slabinfo.py: updated to work on current kernel

slabinfo.py script does not work with actual kernel version.

First, it was unable to recognise SLUB susbsytem, and when I specified
it manually it failed again with

  AttributeError: 'struct page' has no member 'obj_cgroups'

.. and then again with

  File "tools/cgroup/memcg_slabinfo.py", line 221, in main
    memcg.kmem_caches.address_of_(),
  AttributeError: 'struct mem_cgroup' has no member 'kmem_caches'

Link: https://lkml.kernel.org/r/cec1a75e-43b4-3d64-2084-d9f98fda037f@virtuozzo.com
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Tested-by: Roman Gushchin <guro@fb.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: vaverin

tools/cgroup/memcg_slabinfo.py

@@ -128,9 +128,9 @@ def detect_kernel_config():
 
     cfg['nr_nodes'] = prog['nr_online_nodes'].value_()
 
-    if prog.type('struct kmem_cache').members[1][1] == 'flags':
+    if prog.type('struct kmem_cache').members[1].name == 'flags':
         cfg['allocator'] = 'SLUB'
-    elif prog.type('struct kmem_cache').members[1][1] == 'batchcount':
+    elif prog.type('struct kmem_cache').members[1].name == 'batchcount':
         cfg['allocator'] = 'SLAB'
     else:
         err('Can\'t determine the slab allocator')
@@ -193,7 +193,7 @@ def main():
         # look over all slab pages, belonging to non-root memcgs
         # and look for objects belonging to the given memory cgroup
         for page in for_each_slab_page(prog):
-            objcg_vec_raw = page.obj_cgroups.value_()
+            objcg_vec_raw = page.memcg_data.value_()
             if objcg_vec_raw == 0:
                 continue
             cache = page.slab_cache
@@ -202,7 +202,7 @@ def main():
             addr = cache.value_()
             caches[addr] = cache
             # clear the lowest bit to get the true obj_cgroups
-            objcg_vec = Object(prog, page.obj_cgroups.type_,
+            objcg_vec = Object(prog, 'struct obj_cgroup **',
                                value=objcg_vec_raw & ~1)
 
             if addr not in stats: